I like your approach, in fact several people when I started development truly believed that the first 2 years or so, you were only supposed to fix bugs and things like that.
The one problem I see with the approach, and this is an issue with the company not your idea, is that they don't have people to train entry level developers. Most of the senior people I've met are incapable of doing it. They lack real expertise or an ability to effectively communicate and deal with people, or they are simply burned out from it. I've seen a number of places where the senior person is tasked with doing that and it takes up all of the person's time. They get punished for being promoted to that role. Heck I can say that I did for a while too. I took a lower position so I could write code and not deal with all of the politics and stress of leading people.
The one problem I see with the approach, and this is an issue with the company not your idea, is that they don't have people to train entry level developers. Most of the senior people I've met are incapable of doing it. They lack real expertise or an ability to effectively communicate and deal with people, or they are simply burned out from it. I've seen a number of places where the senior person is tasked with doing that and it takes up all of the person's time. They get punished for being promoted to that role. Heck I can say that I did for a while too. I took a lower position so I could write code and not deal with all of the politics and stress of leading people.